KARACHI, Pakistan — Pakistan on Saturday blocked supply routes for U.S.-led troops in Afghanistan and announced it would end the use of a Pakistani airbase by American forces, in retaliation for a NATO attack on a Pakistani border outpost that officials said killed at least 24 soldiers and injured another 13.

American forces were given 15 days to vacate the remote Shamsi airbase, which was secretly turned over to them after the 9/11 attacks. The decision to order the Americans out followed an emergency meeting of Pakistan’s top civilian and military leadership late Saturday to decide how to respond to the deaths of the soldiers.

Shamsi was used for launching the war in Afghanistan in late 2001, then later served as the base for the U.S. drone program targeting militants. Set in desert in sparsely populated Baluchistan province in Pakistan’s west region, the airbase became highly controversial within Pakistan for its association with drone strikes, which Pakistan officially condemns.

The decision to expel the Americans, made by the country’s leadership meeting as the Defense Committee of the Cabinet, was an admission that Shamsi remains in American use.

The committee also announced that the government would “revisit and undertake a complete review of all programs, activities and cooperative arrangements” with the United States and U.S.-led forces in Afghanistan, “including diplomatic, political, military and intelligence.”

Relations between Islamabad and Washington were already under deep strain before the incident, in which helicopters from the International Security Assistance Force (ISAF) operating in Afghanistan shelled checkpoints on the Pakistani side, apparently in error.

“These attacks, which constituted breach of sovereignty, were violative of international law and had gravely dented the fundamental basis of Pakistan’s cooperation with NATO/ISAF against militancy and terror,” said a statement issued late Saturday by the committee, which is chaired by the prime minister and includes the army chief. “NATO/ISAF attacks were also violative of their mandate which was confined to Afghanistan.”

The deaths of the Pakistani soldiers will pour fuel on the already raging anti-American sentiment in this key U.S. ally. Although there have been previous deaths of Pakistani troops caused by mistaken fire from coalition aircraft, the scale of the bloodshed this time was far greater. A statement from the Pakistani army chief, Gen. Ashfaq Kayani, put the death toll at 24. Other reports put the number killed as high as 28.

The border between Pakistan’s tribal area and Afghanistan is poorly marked. Insurgents, who use the tribal area as a safe haven, often fire on coalition and Afghan troops from positions close to Pakistani checkpoints, raising U.S. suspicions that the Pakistani military collaborates with the insurgents.

The attack took place in the early hours of Saturday morning, around 2 a.m. local time, at an outpost on a mountain about 1.5 miles from the border, in the Mohmand part of the tribal area. Mohmand borders both Kunar and Nangarhar provinces in eastern Afghanistan, both areas where the Taliban is active.

The international coalition and the Pakistan military have poor communication at the border and their maps of the border line and the location of Pakistani check points don’t always match.

Pakistan had previously announced that it would expel the Americans from Shamsi, which was never carried out. This time it seemed serious.

While Pakistan officially condemns the operation of U.S. drone aircraft over its territory, it quietly continues to co-operate with aspects of the drone program. It is believed that drones still fly out of Shamsi, but it is unclear whether they are armed or purely surveillance drones now.

Most drone flights now take place from an airbase at Jalalabad in Afghanistan.